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Solar Panels
What's the minimum amps/volts output needed to trickle charge two marine
batteries to keep them up? Can a single small trickle charge panel charge two batteries at the same time? What's the recommended connection method? Need a diode to protect against overcharging (even with a minimum output panel?). Any advice would be appreciated. |
Solar Panels
On Sun, 23 Nov 2003 16:06:53 +0000, Hmseconomy wrote:
What's the minimum amps/volts output needed to trickle charge two marine batteries to keep them up? Can a single small trickle charge panel charge two batteries at the same time? What's the recommended connection method? Need a diode to protect against overcharging (even with a minimum output panel?). Any advice would be appreciated. I'll start with an assumption that may be wrong, but...Assume a battery loses 50% of its charge in 3 months, and it's about 80AH. That means it loses about .4 AH per day. So it needs about .4 amps CONTINUOUSLY to keep it charged. Now, since a solar panel only puts out anything about 50% of the time (assume full sun all day) you would need an 800mA panel. But a "1 Amp" panel only puts out close to 1 amp in full sun when the sun's directly perpendicular to the cell, I'd put it a 60-70% "fudge factor" (more if you live in a cloudy area). This means you need about a 1.3A panel per battery. Note that most of these "trickle charge" solar panels only put out 200mA or so. Also, a diode is so that the battery doesn't "backfeed" the panel, not to prevent overcharging. Based on this, I'd say you'd be safe with a 2A panel, paralleled to both batteries (assuming there's no load on the batteries). I've used a 2A panel on one 4D battery over the summer, and it seemed to work well. I doubt one of these "trickle charge" panels would be useful for the long term. Lloyd Sumpter "Far Cove" Catalina 36 |
Solar Panels
On Sun, 23 Nov 2003 16:06:53 +0000, Hmseconomy wrote:
What's the minimum amps/volts output needed to trickle charge two marine batteries to keep them up? Can a single small trickle charge panel charge two batteries at the same time? What's the recommended connection method? Need a diode to protect against overcharging (even with a minimum output panel?). Any advice would be appreciated. I'll start with an assumption that may be wrong, but...Assume a battery loses 50% of its charge in 3 months, and it's about 80AH. That means it loses about .4 AH per day. So it needs about .4 amps CONTINUOUSLY to keep it charged. Now, since a solar panel only puts out anything about 50% of the time (assume full sun all day) you would need an 800mA panel. But a "1 Amp" panel only puts out close to 1 amp in full sun when the sun's directly perpendicular to the cell, I'd put it a 60-70% "fudge factor" (more if you live in a cloudy area). This means you need about a 1.3A panel per battery. Note that most of these "trickle charge" solar panels only put out 200mA or so. Also, a diode is so that the battery doesn't "backfeed" the panel, not to prevent overcharging. Based on this, I'd say you'd be safe with a 2A panel, paralleled to both batteries (assuming there's no load on the batteries). I've used a 2A panel on one 4D battery over the summer, and it seemed to work well. I doubt one of these "trickle charge" panels would be useful for the long term. Lloyd Sumpter "Far Cove" Catalina 36 |
Solar Panels
I don't know where your numbers come from - the OP didn't mention a battery
size. But more importantly, your number of 80 AmpHours for 3 months implies about 1 AH per day, This cold be handled by a 5 Watt panel such as this one featured on the Boat/US site. It has a built in diode. http://www.boatus-store.com/webapp/w...roductId=56290 Since the winter sun is not very strong, and the sky might be cloudy, this might be on the small size for a larger bank, so you would be well advised to visit monthly to make sure they are staying charged. You might consider getting a "full size panel" and a regulator. These will collect enough light even through shrink wrap to keep a large bank charged, and will be useful in the summer. "Lloyd Sumpter" wrote in message ... On Sun, 23 Nov 2003 16:06:53 +0000, Hmseconomy wrote: What's the minimum amps/volts output needed to trickle charge two marine batteries to keep them up? Can a single small trickle charge panel charge two batteries at the same time? What's the recommended connection method? Need a diode to protect against overcharging (even with a minimum output panel?). Any advice would be appreciated. I'll start with an assumption that may be wrong, but...Assume a battery loses 50% of its charge in 3 months, and it's about 80AH. That means it loses about ..4 AH per day. So it needs about .4 amps CONTINUOUSLY to keep it charged. Now, since a solar panel only puts out anything about 50% of the time (assume full sun all day) you would need an 800mA panel. But a "1 Amp" panel only puts out close to 1 amp in full sun when the sun's directly perpendicular to the cell, I'd put it a 60-70% "fudge factor" (more if you live in a cloudy area). This means you need about a 1.3A panel per battery. Note that most of these "trickle charge" solar panels only put out 200mA or so. Also, a diode is so that the battery doesn't "backfeed" the panel, not to prevent overcharging. Based on this, I'd say you'd be safe with a 2A panel, paralleled to both batteries (assuming there's no load on the batteries). I've used a 2A panel on one 4D battery over the summer, and it seemed to work well. I doubt one of these "trickle charge" panels would be useful for the long term. Lloyd Sumpter "Far Cove" Catalina 36 |
Solar Panels
I don't know where your numbers come from - the OP didn't mention a battery
size. But more importantly, your number of 80 AmpHours for 3 months implies about 1 AH per day, This cold be handled by a 5 Watt panel such as this one featured on the Boat/US site. It has a built in diode. http://www.boatus-store.com/webapp/w...roductId=56290 Since the winter sun is not very strong, and the sky might be cloudy, this might be on the small size for a larger bank, so you would be well advised to visit monthly to make sure they are staying charged. You might consider getting a "full size panel" and a regulator. These will collect enough light even through shrink wrap to keep a large bank charged, and will be useful in the summer. "Lloyd Sumpter" wrote in message ... On Sun, 23 Nov 2003 16:06:53 +0000, Hmseconomy wrote: What's the minimum amps/volts output needed to trickle charge two marine batteries to keep them up? Can a single small trickle charge panel charge two batteries at the same time? What's the recommended connection method? Need a diode to protect against overcharging (even with a minimum output panel?). Any advice would be appreciated. I'll start with an assumption that may be wrong, but...Assume a battery loses 50% of its charge in 3 months, and it's about 80AH. That means it loses about ..4 AH per day. So it needs about .4 amps CONTINUOUSLY to keep it charged. Now, since a solar panel only puts out anything about 50% of the time (assume full sun all day) you would need an 800mA panel. But a "1 Amp" panel only puts out close to 1 amp in full sun when the sun's directly perpendicular to the cell, I'd put it a 60-70% "fudge factor" (more if you live in a cloudy area). This means you need about a 1.3A panel per battery. Note that most of these "trickle charge" solar panels only put out 200mA or so. Also, a diode is so that the battery doesn't "backfeed" the panel, not to prevent overcharging. Based on this, I'd say you'd be safe with a 2A panel, paralleled to both batteries (assuming there's no load on the batteries). I've used a 2A panel on one 4D battery over the summer, and it seemed to work well. I doubt one of these "trickle charge" panels would be useful for the long term. Lloyd Sumpter "Far Cove" Catalina 36 |
Solar Panels
Lloyd Sumpter wrote: I'll start with an assumption that may be wrong, but...Assume a battery loses 50% of its charge in 3 months, and it's about 80AH. That means it loses about .4 AH per day. So it needs about .4 amps CONTINUOUSLY to keep it charged. Lloyd, sorry to have to point it out, but there's an error in your statement. .4 amps continuously is .4 x 24 hours/day = 9.6 AH per day. Taking your assumption of having to produce 80 AH during a three month period and assumming that the panel is only charging an average of 8 hours per day, you'd only need to develope 55ma (.055 amps) from the solar panel to maintain the charge. (80 AH / 182 days / 8 hours per day = .055 Amps) -- Dan Best - (707) 431-1662, Healdsburg, CA 95448 B-2/75 1977-1979 Tayana 37 #192, "Tricia Jean" http://rangerbest.home.comcast.net/TriciaJean.JPG |
Solar Panels
Lloyd Sumpter wrote: I'll start with an assumption that may be wrong, but...Assume a battery loses 50% of its charge in 3 months, and it's about 80AH. That means it loses about .4 AH per day. So it needs about .4 amps CONTINUOUSLY to keep it charged. Lloyd, sorry to have to point it out, but there's an error in your statement. .4 amps continuously is .4 x 24 hours/day = 9.6 AH per day. Taking your assumption of having to produce 80 AH during a three month period and assumming that the panel is only charging an average of 8 hours per day, you'd only need to develope 55ma (.055 amps) from the solar panel to maintain the charge. (80 AH / 182 days / 8 hours per day = .055 Amps) -- Dan Best - (707) 431-1662, Healdsburg, CA 95448 B-2/75 1977-1979 Tayana 37 #192, "Tricia Jean" http://rangerbest.home.comcast.net/TriciaJean.JPG |
Solar Panels
Lloyd's estimate started out strong, with an estimate of 0.4 amp hours
of trickle per day. But that means 0.4 amps for ONE hour per day So a 1/8 amp panel at 14 volts (for 3 or 4 hours per day) would do the job for each battery. Brian Whatcott Altus OK On Sun, 23 Nov 2003 08:41:51 -0800, "Lloyd Sumpter" wrote: On Sun, 23 Nov 2003 16:06:53 +0000, Hmseconomy wrote: What's the minimum amps/volts output needed to trickle charge two marine batteries to keep them up? Can a single small trickle charge panel charge two batteries at the same time? What's the recommended connection method? Need a diode to protect against overcharging (even with a minimum output panel?). Any advice would be appreciated. I'll start with an assumption that may be wrong, but...Assume a battery loses 50% of its charge in 3 months, and it's about 80AH. That means it loses about .4 AH per day. So it needs about .4 amps CONTINUOUSLY to keep it charged. Now, since a solar panel only puts out anything about 50% of the time (assume full sun all day) you would need an 800mA panel. But a "1 Amp" panel only puts out close to 1 amp in full sun when the sun's directly perpendicular to the cell, I'd put it a 60-70% "fudge factor" (more if you live in a cloudy area). This means you need about a 1.3A panel per battery. Note that most of these "trickle charge" solar panels only put out 200mA or so. Also, a diode is so that the battery doesn't "backfeed" the panel, not to prevent overcharging. Based on this, I'd say you'd be safe with a 2A panel, paralleled to both batteries (assuming there's no load on the batteries). I've used a 2A panel on one 4D battery over the summer, and it seemed to work well. I doubt one of these "trickle charge" panels would be useful for the long term. Lloyd Sumpter "Far Cove" Catalina 36 |
Solar Panels
Lloyd's estimate started out strong, with an estimate of 0.4 amp hours
of trickle per day. But that means 0.4 amps for ONE hour per day So a 1/8 amp panel at 14 volts (for 3 or 4 hours per day) would do the job for each battery. Brian Whatcott Altus OK On Sun, 23 Nov 2003 08:41:51 -0800, "Lloyd Sumpter" wrote: On Sun, 23 Nov 2003 16:06:53 +0000, Hmseconomy wrote: What's the minimum amps/volts output needed to trickle charge two marine batteries to keep them up? Can a single small trickle charge panel charge two batteries at the same time? What's the recommended connection method? Need a diode to protect against overcharging (even with a minimum output panel?). Any advice would be appreciated. I'll start with an assumption that may be wrong, but...Assume a battery loses 50% of its charge in 3 months, and it's about 80AH. That means it loses about .4 AH per day. So it needs about .4 amps CONTINUOUSLY to keep it charged. Now, since a solar panel only puts out anything about 50% of the time (assume full sun all day) you would need an 800mA panel. But a "1 Amp" panel only puts out close to 1 amp in full sun when the sun's directly perpendicular to the cell, I'd put it a 60-70% "fudge factor" (more if you live in a cloudy area). This means you need about a 1.3A panel per battery. Note that most of these "trickle charge" solar panels only put out 200mA or so. Also, a diode is so that the battery doesn't "backfeed" the panel, not to prevent overcharging. Based on this, I'd say you'd be safe with a 2A panel, paralleled to both batteries (assuming there's no load on the batteries). I've used a 2A panel on one 4D battery over the summer, and it seemed to work well. I doubt one of these "trickle charge" panels would be useful for the long term. Lloyd Sumpter "Far Cove" Catalina 36 |
Solar Panels
On Sun, 23 Nov 2003 19:53:54 +0000, Daniel E. Best wrote:
Lloyd Sumpter wrote: I'll start with an assumption that may be wrong, but...Assume a battery loses 50% of its charge in 3 months, and it's about 80AH. That means it loses about .4 AH per day. So it needs about .4 amps CONTINUOUSLY to keep it charged. Lloyd, sorry to have to point it out, but there's an error in your statement. .4 amps continuously is .4 x 24 hours/day = 9.6 AH per day. Oops - I stand corrected! Chalk it up to not enough coffee. Lloyd |
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